Add external library freetype2

Created configure script which writes
the freetype2 configuration in projekte/external-lib/freetype2
with information gathered from 'freetype-config'.

The freetype2 library will be included from projekte/subsys/graphic.
The graphic subsystem is used by unittest.prj and demo.prj.

The freetype library will allow the OpenGL ES graphic subsystem
to draw text. To support other scripts than Latin additional
libraries like HarfBuzz will be needed as well.
Protect include command in genmake

The include command of the makefile generation tool genmake was changed.
Now every file is included only once even if it is included more than
once.

This allows to include external libraries from within subsystems
even if more than one subsystem needs the same library.

Include of external library freetype2 is moved into graphic subsystem.
Removed GLX OpenGL binding to X11

The OpenGL EGL interface is used to bind the native window system
to OpenGL. This is portable across operating systems. The GLX
binding was specific to the X11 window system.
Rename KONFIG values for KONFIG_LANG

They are renamed from KONFIG_en to en and KONFIG_de to de.
Rename startup.h into init.h

The platform specific init function startup_platfrom was renamed
into init_platform.
Add new validation routine to testmm_t

The test memory manager testmm_t got a new
validation function isvalidtrailer_testmmblock
which checks that a block trailer is valid
before an already freed block is merged with
the current block during the execution of freeblock_testmmpage.
Implement point_texture_demo.c

Demo draws a rectangle containing a texture (image).
Also the same texture is drawn on points with a size
of 32 pixel. Points with a texture painted on them
are also called point sprites.
Renamed module mm_test into err_macros.

Also the error macros are renamed from ALLOC_TEST into ALLOC_ERR_MM.

* Renamed
     // group: variables
  into
     // group: static variables
  or
     // group: global variables

* Corrected error in RESIZE_ERR_MM, FREE_ERR_MM, and ALLOC_ERR_MM.
Update auf Ubuntu 14.04 LTS

Replace log_it.clearbuffer with log_it.truncatebuffer.
The function truncatebuffer allows for a finer control
of resetting the buffer.

Also removed signed overflow and other warnings.